Modular divisible barrel-shaped shell for metallurgical furnaces

ABSTRACT

The disclosed horizontally divisible furnace shell comprises a spherically shaped bottom section and truncated cone cover-like shaped middle and top wall sections stacked upon the bottom section, the form of the middle and top sections resulting in barrel-shaped shell walls. Each of the three modular sections has a metal casing with a refractory lining which may be made of firebrick or fireclay. Each wall section has an inwardly projecting ledge at its lower end for supporting the refractory lining. For interconnecting and aligning the sections, tapered locating pins and sockets are provided between all sections. Water-cooled flanges are preferably provided at the upper and lower ends of the top wall section. The joint between the middle and top wall sections is stepped upwardly adjacent the pouring spout so that such joint will be above the level of the molten metal, even when the furnace is tilted to pour out the metal. The middle wall section is provided with a molten metal discharge opening and a pouring spout extending outwardly beneath such opening. At least one slag discharge opening is formed in the middle and top wall sections. Modular removable water-cooled members are provided along the sides and the top of such slag discharge opening. A movable water-cooled heat resistant door is provided to close the slag discharge opening. Beneath the slag discharge opening, the middle wall section is provided with an apron which preferably has refractory material in the form of graphite blocks to prevent the slag from adhering to the apron. The bail for lifting and transporting the separate modular shell sections has a non-symmetrical shape and adjustable links, such shape being adapted to accommodate the middle and top wall sections, which have different lifting point locations and different centers of gravity. Using the lifting bail, the entire middle or top wall section, complete with its refractory lining, may then be lifted from the furnace or into place on the furnace. Thus, the worn-out refractory lining may be removed from the shell section, and the new lining may be installed when the wall section is dismounted from the furnace. It is preferred to provide spare wall sections so that they can be fitted with new refractory linings while the furnace is operating. The replacement of the used wall section or sections having worn-out refractory linings with the spare wall section or sections having new refractory linings may be performed quickly, with only a short shutdown of the furnace.

United States Wunsche atent [191 [75] Inventor: Edgar Wunsche, Oshawa,Ontario,

Canada [73] Assignees Engineered Metal Products.

amnwinalirmiashamA [22] Filed: Aug. 2, 1972 [21] Appl. No.: 277,142

[52] US. Cl 266/35, 266/43, 13/10, I 13/35 [51] Int. Cl. C210 5/44 [58]Field of Search 13/10, 32-35; 266/39, 35, 43

[56] References Cited UNITED STATES PATENTS 395,434 1/1889 Gordon 266/35432,280 7/1890 Nenninger 266/40 900,291 10/1908 Meissner 266/35 929,5987/1909 Keep 266/25 1,225,232 5/1917 Fischer.. 266/25 1,297,149 3/1919Greene.. 13/10 1,304,350 5/1919 Moore 13/10 1,352,040 9/1920VonSchlegell et al.... 13/10 1,445,860 2/1923 Turek 13/35 1,514,26811/1924 Stewart 13/10 2,101,391 12/1937 Grotewohl 266/25 2,202,2245/1940 Moore 13/10 2,493,642 l/l950 Renshaw et al.... 266/43 2,828,5164/1958 Black et al..... 266/37 2,938,782 5/1960 Toulmin 266/25 3,148,9739/1964 Holowaty et a1... 266/25 3,211,443 10/1965 Starner et a1. 266/393,403,213 9/1968 Taylor et al. 266/43 3,429,973 2/1969 Carter et a113/32 OTHER PUBLICATIONS Publication: Iron & Steel Engineer; May 1946;pages 60-67.

Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-Burmeister,lPalmatier & Hamby 57] ABSTRACT The disclosed horizontally divisiblefurnace shell comprises a spherically shaped bottom section and trun- 1Mar. 18, 1975 cated cone cover-like shaped middle and top wall sectionsstacked upon the bottom section, the form of the middle and top sectionsresulting in barrel-shaped shell walls. Each of the three modularsections has a metal casing with a refractory lining which may be madeof firebrick or fireclay. Each wall section has an inwardly projectingledge at its lower end for supporting the refractory lining. Forinterconnecting and aligning the sections, tapered locating pins andsockets are provided between all sections. Water-cooled flanges arepreferably provided at the upper and lower ends of the top wall section.The joint between the middle and top wall sections is stepped upwardlyadjacent the pouring spout so that such joint will be above the level ofthe molten metal, even when the furnace is tilted to pour out the metal.The middle wall section is provided with a molten metal dischargeopening and a pouring spout extending outwardly beneath such opening. Atleast one slag discharge opening is formed in the middle and top wallsections. Modular removable water-cooled members are provided along thesides and the top of such slag discharge opening. A movable water-cooledheat resistant door is provided to close the slag discharge opening.Beneath the slag discharge opening, the middle wall section is providedwith an apron which preferably has refractory material in the form ofgraphite blocks to prevent the slag from adhering to the apron. The bailfor lifting and transporting the separate modular shell sections has anonsymmetrical shape and adjustable links, such shape being adapted toaccommodate the middle and top wall sections, which have differentlifting point locations and different centers of gravity. Using thelifting bail, the entire middle or top wall section, complete with itsrefractory lining, may then be lifted from the furnace or into place onthe furnace. Thus, the wornout refractory lining may be removed from theshell section, and the new lining may be installed when the wall sectionis dismounted from the furnace. It is preferred to provide spare wallsections so that they can be fitted with new refractory linings whilethe furnace is operating. The replacement of the used wall section orsections having worn-out refractory linings with the spare wall sectionor sections having new refractory linings may be performed quickly, withonly a short shutdown of the furnace.

12 Claims, 17 Drawing Figures PAIEMED 1 8 i975 sum 2 BF. 6

PAI EHTEU I 197s I 3.871.632 sum 3 or 5 FIG, 6 I

PATENTEU R 1 19.75

sutnu'nrs 8cm MQQQ MODULAR DIVISIBLE BARREL-SHAPED SHELL FORMETALLURGICAL FURNACES This invention relates to a furnace shell for usewith molten metal. For example, the furnace shell may'be employed tomelt steel scrap and for many other applications.

One object of the present invention is to provide an improved furnaceshell which is modular in that it is made up of a plurality of sectionsor components which can readily be removed from the furnace formaintenance or replacement.

A further object is to provide such an improved furnace shell whichrequires only a very brief shutdown to repair or replace the refractorylining of the entire wall of the furnace.

Another object is to provide an improved furnace shell which isbarrelshaped at the middle and top wall sections, and thus is bulgedoutwardly to a diameter greater than that of the bottom section, andalso greater than the upper diameter of the top section where the roofring rests on the shell. Besides providing more charging volumecapacity, the barrel shape of the middle and top wall sections provideslonger refractory life, especially in so-called hot spots,, because ofincreased distance between the electric arcs and the wall refractorylining, and therefore more uniform and lower thermal stress per squareunit of refractory area. The barrel-shaped middle and top wall sectionshave the further advantage of decreasing the mechanical stress on lowerbrick courses because a part of the gravitational load is borne by theupwardly flaring conical metal casing of the shell. An added advantageof the barrel-shaped middle and top wall sections resides in the factthat the patching material, which is thrown against the walls by hand ormechanically, stays much better in the desired place because of theoutward conicity of the refractory lining in the most commonly patchedor repaired area. Furthermore, the barrelshaped middle and top sectionsresult in more uniform thermal stress along the entire inside surface ofthe refractory lining, allowing usage of a thinner refractory lining atthe upper part of the top wall section. As a further advantage, thebarrel-shaped middle and top wall sections result in longer roofrefractory life because of more uniform thermal stress caused by widespreading of reflected heat radiation by the barrel-shaped walls overthe entire inside surface of the roof.

In accordance with the present invention, the improved furnace shell ispreferably modular in that it comprises two wall sections which can beseparated when it is desired to do maintenance work on the sections.Preferably, the furnace comprises three exchangeable sections includinga bottom section, a mid dle wall section, and a top wall section. Thebottom section is preferably spherically shaped, while the wall sectionsare generally truncated cone cover-like shaped. Each section preferablycomprises a metal casing and a refractory lining mounted therein. Thelining may be made of flrebricks, fireclay or other refractorymaterials.

When it is necessary to replace the worn-out refractory lining of thefurnace, either partially or entirely, the top wall section may beremoved from the furnace. The middle wall section may also be removed asneeded. It is preferred to provide spare sections which are fitted withrefractory linings before the furnace is taken out of service. Tosupport the refractory linings, the wall sections are preferablyprovided with inwardly projecting ledges or flanges adjacent their lowerends.

After the old sections have been removed from the furnace, the spacesections may be lifted, complete with their refractory linings, and maybe mounted on the furnace. The horizontal joints between the newrefractory linings of the three sections are then filled and sealed withrefractory material such as fireclay. The prelined sections can beassembled on the furnace in much less time than would be required toreplace the refractory lining of the furnace, without any provision forseparating the furnace into sections.

An improved reversible bail is preferably provided for lifting andtransporting the separate modular shell sections. The bail preferablyhas a non-symmetrical shape and adjustable links so that the bail isadapted to accommodate the middle and top wall sections, which havedifferent lifting point locations and different centers of gravity.

The horizontal joint between the bottom section and the middle sectionis preferably below the normal slag line, while the joint between themiddle and top wall sections is preferably above the slag line. It ispreferred to construct the wall sections so that the joint between thewall sections has a rectangular step. The upper level of the step isadjacent the discharge opening through which the molten metal is pouredout of the furnace, while the lower level of the step is positioned awayfrom the discharge opening. in this way, the joint remains above theslag line when the furnace is tilted or rocked to pour out the moltenmetal.

Preferably, the top wall section has upper and lower border flangeswhich are hollow to provide passages through which cooling water or someother fluid collant may be circulated. The top section is formed with anopening or openings through which excess slag may be poured out. Suchopening may be lined with a plurality of removable members havingpassages therein through which cooling water or some other fluid coolantmay be circulated. A movable door is preferably provided to close theslag discharge opening. The door may also have passages therein for thecirculation of a fluid coolant.

The middle wall section is preferably provided with a pouring spoutprojecting outwardly therefrom beneath the discharge opening for themolten metal. The spout preferably comprises a metal structure which isremovably mounted on the middle wall section so that it can be replacedas needed. A refractory lining may be mounted in the metal structure ofthe pouring spout.

The middle wall section also preferably comprises an apron or sill whichprojects outwardly therefrom beneath the slag discharge opening. Suchapron preferably comprises a removable metal shell which supports arefractory lining, preferably in the form of graphite blocks having highheat conductivity. This construction has the advantage that the slag andmetal will not adhere to the graphite material.

Further objects, advantages and features of the present invention willappear from the following description, taken with the accompanyingdrawings, in which:

FIG. 1 is a central vertical section taken through a modular furnaceshell to be described as an illustrative embodiment of the presentinvention.

FIG. 2 is a perspective view showing the bottom section of the furnaceshell.

FIG. 3 is a perspective view showing the middle or intermediate wallsection with the pouring spout in a detached position.

FIG. 4 is a perspective view showing the top wall section of the furnaceshell, with the door, the apron,.and

the components for lining the slag discharge opening in detachedpositions.

FIG. 5 is a central vertical section, similar to FIG. 1 but with therefractory lining removed from the furnace shell.

FIG. 6 is a fragmentary side elevation of the furnace shell lookingtoward the pouring spout for the molten metal.

FIG. 7 is a fragmentary view of the opposite side, looking toward theslag discharge opening.

FIG. 8 is a fragmentary plan view of the furnace shell.

FIG. 9 is an enlarged vertical section taken through 32. Fireclay orsome other heat-resistant material may I be employed to complete therefractory lining 30.

The bottom section 22 of the furnace shell 20 is supported in any knownor suitable manner so that the furnace shell may be tipped or rocked topour out the molten metal. The illustrated metal shell 28 has a smoothlyrounded bottom portion 34 to provide for the rocking or tilting of thefurnace shell.

The middle wall section 24 of the furnace shell 20 is generallyring-shaped and is also provided with a metal casing or shell 36 (FIGS.5-7) having a refractory lining 38, which may be made of firebricks andfireclay, or any other known or suitable refractory material.

The top wall section 26 is also ring-shaped. It comprises a metal casingor shell 40 having a refractory lining 42 which may be made offirebricksand fireclay or any other suitable refractory materials.

It will be seen from FIGS. 1 and 5 that the wall sections 24 and 26 arebarrel-shaped in that they bulge outwardly to a diameter greater thanthat of the bottom section 22, and also greater than the upper diameterof the pouring spout, detached from the furnace shell, the

view being taken generally as indicated by the line 13-13 in FIG. 12.

FIG. 14 is a plan view of the metal structure for the pouring spout.

FIG. 15 is a plan view of an improved bail which may be employed forlifting themiddle and top wall sections of the furnace shell.

FIGS. 16 and 17 are front and side elevations of the bail of FIG. 15.

It will be understood that the drawings and the following descriptionare merely illustrative in that they disclose a particularly meritoriousembodiment of the present invention.

As just indicated, FIG. 1 illustrates a furnace shell 20 for use withmolten metal. For example, the furnace shell 20 may be employed to meltsteel scrap or other metals. The furnace shell 20 is adaptable to manyother uses.

As shown in FIG. 1, the furnace shell 20 has a bottom section 22 andmiddle and top wall sections 24 and 26 stacked upon the bottom section22. Thus, the middle wall section 24 is mounted on top of the bottomsection 22, while the top, wall section 26 is mounted on top of themiddle wall section 24. It will be understood that the top wall section26 is adapted to support a cover or roof section, which may be of anyknown or suitable construction. The heat to melt the metal in thefurnace may be supplied by electric arcs between electric arcelectrodes, projecting downwardly into the furnace through openings inthe roof section in a manner which will be familiar to those skilled inthe art.

It will be seen from FIG. 1 that the bottom section 22 is generallyspherically shaped and is formed with a metal casing or shell 28 havinga refractory lining 30. Any known or suitable material may be employedin the refractory lining, such as the illustrated firebricks the topsection 26. Thus, the middle or intermediate wall section 24 isgenerally frusto-conical in shape and flares outwardly in diameterbetween its lower and upper ends. The top wall section 26 flaresoutwardly and then tapers inwardly between its lower and upper ends.Thus, the metal casing 40 of the top section 26 has a generallyfrusto-conical lower portion 44 which tapers downwardly and a generallyfrusto-conical upper portion 46 which tapers upwardly. As previouslymentioned, it is advantageous to make the wall sections 24 and 26barrel-shaped because the capacity of the furnace shell and its abilityto withstand heat are thereby increased. The barrel shape of the wallsections provides more room for refractory material and a greater volumein the upper portion of the furnace shell where it is subjected to theintense heat of the electric arcs.

It will be evident from FIGS. 1 and 2 that the metal shell 28 of thebottom section 22 is formed at its upper end with a substantiallyhorizontal outwardly projecting flange 48 adapted to be engaged by asimilar outwardly projecting substantially horizontal flange 50 on thelower end of the metal shell 36 of the first or middle wall section 24.Locating elements are preferably vprovided on the bottom section 22 andthe middle wall section 24 to align the middle wall section with thebottom section and to prevent any change in such alignment when thefurnace shellis tipped to pour the molten metal therefrom.

As shown in FIG. 2, such locating elements may take the form of pins 52projecting upwardly fromthe horizontal flange 48 on the bottom section22. The illustrated pins 52 are conically tapered. The pins 52 interlockwith mating elements on the middle wall section 24. As shown in FIG. 11,such mating elements may take the form of tapered socket member 54'secured in suitable openings formed in the flange 50 on the middle wallsection 24.

When the furnace shell 20 is in use, a pool of molten metal is containedwithin the bottom section 22 and the lower portion of the middle wallsection 24 of the furnace shell 20. In most cases, a thin layer of slagwill float on the surface of the molten metal. A typical level for theslag is indicated by a slag line 56 in FIG. 1. It will be noted that theslag line 56 is above the joint between the bottom section 22 and themiddle wall section 24. It will be understood that the joint between thesections 22 and 24 is sealed by fireclay or some other suitablerefractory material applied between the refractory lining of the bottomsection 22 and the refractory lining 38 of the middle wall section 24.

It will be evident from FIGS. 1 and 2 that a discharge opening 58 forthe molten metal is formed through one side portion of the middle wallsection 24. The refractory lining 38 of the wall section 24 extends intothe discharge opening 58 so that it is completely lined by refractorymaterial.

A pouring spout 60 is preferably provided on the middle wall section 24to receive the molten metal from the discharge opening 58. Theillustrated pouring spout 60 comprises a tapered generally trough-shapedmetal structure or shell 62 which is provided with a refractory lining64 made of firebricks and fireclay or other suitable refractorymaterials.

Preferably, the metal structure 62 of the pouring spout 60 is removablymounted on the metal casing 28 of the bottom section 22 so that thestructure 62 of the spout 60 can readily be removed and replaced. Asshown in FIG. 5, the metal structure 62 of the spout 60 is formed withinclined flanges 66 adapted to engage mating flanges 68 on the metalcasing 36 of the middle wall section 24.

Horizontal flange elements or tabs 70 are also preferably provided onthe metal structure 62 of the pouring spout 60 and are adapted to engagea horizontal flange 72 on the upper end of the middle wall section 24.Locating elements are preferably arranged to extend between the flangeelements 70 and the flange 72.

As shown to best advantage in FIGS. 12 and 13, such locating elementspreferably include tapered pins 74 projecting downwardly from the flangeelement 70. Openings 76 are preferably formed in the flange 72 on thewall section 24 to receive the pins 74. It will be evident that themetal structure 62 of the spout 60 may be mounted on the middle wallsection 24 by lowering the structure 62 into place so that the pins 74are inserted through the openings 76. Bolts or other fasteners 78 maythen be employed to secure the flanges 66 and 68 together. If thepouring spout 60 is damaged by heat or otherwise, it can be replacedquickly and readily.

It is preferred to form the middle wall section 24 with a stepped upperend portion. As will be evident from FIG. 3, the horizontal flange 72,previously mentioned in connection with FIG. 5, is stepped above a pairof horizontal flange elements 80 mounted on the upper end of the middlewall section 24. The flange 72, constituting the upper step, is adjacentthe discharge opening 58, while the flange elements 80, constituting thelower step, are more remote therefrom.

This stepped construction has the important advantage that the jointbetween the middle and upper wall sections 24 and 26 is always above theslag line 56, even when the furnace shell 20 is tilted to pour out themolten metal through the discharge opening 58. The stepped constructionmakes it easy to fit firebricks into the wall sections 24 and 26 whenthe refractory linings 38 and 42 are being installed.

As will be evident from FIG. 4, the lower end of the top wall section 26is similarly stepped to mate with the stepped upper end of the middlewall section 24. As shown, the lower end of the top wall section 26 isprovided with an upwardly stepped flange 82 to mate with the flange 72and downwardly stepped flange elements 84 to mate with the flangeelements 80.

Locating elements are preferably provided between the middle and topwall sections 24 and 26 to maintain alignment between the sections. Asbefore, such locating elements preferably take the form of tapered pins86 projecting upwardly from the middle wall section 24. Tapered socketmembers 88 are preferably provided on the top wall section 26 to receivethe pins 86, as shown in FIG. 11.

The refractory lining of the furnace shell 20 has only a limited life sothat it is necesssry to replace the refractory lining after the furnacehas been in operation for a period of time. The furnace shell 20 must betaken out of service and shutdown in order to replace the refractorylining. To minimize the shutdown time, it is preferred to provide sparesfor the middle and top wall sections 24 and 26 of the furnace shell.While the furnace shell is in operation, using the original wallsections 24 and 26, the spares are provided with their refractorylinings 38 and 42.

When it is necessary to shut down the furnace, the original wallsections 24 and 26 are removed from the furnace shell and the spares arehoisted into place complete with their refractory linings 38 and 42.Generally, the refractory lining 30 of the bottom section 22 willoutlast several refractory linings for the wall sections 24 and 26,which are subjected to more intense heat and greater thermal shock.Thus, during the usual shutdown, it is not necessary to replace therefractory lining 30 of the bottom section 22. It is simply necessary tohoist the spare wall sections 24 and 26 into place complete with theirrefractory linings 38 and 42. Fireclay or other refractory material isthen employed to seal the joints between the refractory linings 30, 38and 42.

In order that the shutdown time of the furnace shell 20 may be minimizedin this advantageous manner, the wall sections 24 and 26 are providedwith means for supporting the refractory linings 38 and 42, even whenthe wall sections are dismounted from the furnace so that the refractorylinings can be installed when the wall sections 24 and 26 aredismounted. As shown in FIGS. 3-5, such means may take the form ofledges 90, 92 and 94 projecting inwardly from the lower ends of the wallsections 24 and 26. The ledge 90 is on the lower end of the middle wallsection 24, while the ledges 92 and 94 are on the upwardly anddownwardly stepped portions at the lower end of the top wall section 26.

When the refractory linings 38 and 42 are installed, the firebricks arelaid upon the ledges 90, 92 and 94. Thus, the refractory linings 38 and42 are securely supported within the wall sections 24 and 26 so thatthey can be hoisted into place on the furnace without damaging therefractory linings. The joints between the three sections 22, 24 and 26are sealed by employing fireclay or some other refractory material tofill the spaces between the refractory linings 30, 38 and 42 of thethree sections.

It will be seen from FIG. 1 that the illustrated furnace shell 20 isprovided with a slag discharge opening 100, which, in this case, isformed primarily in the top wall section 26, but also is formed to someextent in the extreme upper portion of the middle wall section 24diametrically opposite from the discharge opening 58 for the moltenmetal. A movable door 102 is preferably provided to close the slagdischarge opening 100. In

this case, the door 102 is positioned at a small angle to the verticaland is slidable upwardly to open the opening 100.

In the illustrated construction as shown to best advantage in FIG. 4,the slag discharge opening 100 is lined by side members 104 and 106 anda top member 108, all of which are removable from the top wall section26 so that the members 104, 106 and 108 can be removed and replaced asneeded. The members 104, 106 and 108 are preferably made of metal andare hollow to provide passages therein for the circulation 9 water orsome other fluid coolant.

The lower side of the slag discharge opening 100" is formed by a sill110 on the metal shell 28 of the bottom section 22. The sill 110 may belined with a suitable refractory material 112 such as firebricks,fireclay or the like.

A refractory or heat-resistant apron 114 is preferably provided on theoutside of the furnace shell 20 beneath the slag discharge opening 110,the apron 114 being positioned so that the molten slag will flow overthe apron 114 when the slag is discharged out of the furnace shell 20through the opening 100. When the slag is to be discharged, the door 102is opened. The furnace shell 20 may then be tilted slightly to cause theslag to pour out of the furnace shell through the opening 100. Thefurnace shell is not tilted sufficiently to allow any of the moltenmetal to escape.

In this case, the apron 114 comprises a metal supporting structure orshell 116 with a refractory lining 118, which may be made of variousmaterials but is preferably made of graphite. The use of graphite hasthe advantage that the slag will not stick to the graphite material. Asshown, the graphite refractory lining 118 is in the form of graphiteblocks supported by the metal structure 116. Preferably, the metalstructure 116 is readily removable from the wall section 24 so that itcan be replaced as needed.

The door 102 is also of a heat-resistant construction. As shown in FIG.9, the door 102 preferably comprises a metal frame 120 having arefractory lining 122, which may be made of firebricks, fireclay or thelike. The illustrated metal frame 120 is hollow to provide passages forthe circulation of cooling water or some other fluid coolant.

Fluid coolant passages may also be provided in the metal casing of thefurnace shell 20, particularly in the metal casing 40 of the top wallsection 26. As shown in FIG. 1, the metal casing 40 of the top wallsection 26 has a border flange 124 which extends around the outside ofthe metal casing 40 at its upper end. The flange 124 is hollow toprovide a circumferential passage 126 for cooling water or some otherfluid coolant.

As shown in FIG. 1, the metal casing 40 of the upper wall section 26also has an outwardly projecting border flange 128 which extends aroundthe lower portion of the metal casing 40 at the level of the upper step82. As shown, the flange 128 is provided with inclined reinforcingplates 130 which extend between the flange 128 and the circumferentialwall 132 of the metal casing 40 to form a circumferential passage 134for the circulation of cooling water or some other fluid coolant.

Additional cooling means may be provided on the metal casing 40 of thetop wall section 26 at the level of the lower step 84. As shown in FIGS.4 and 11, additional outwardly projecting border flanges 136 areprovided on the metal casing 40 at the level of the lower step 84. Thereare two of the flanges 136 on opposite sides of the slag dischargeopening 100. Reinforcing plates 138 are welded or otherwise securedbetween the flanges 136 and the circumferential wall 132 to formpassages 140 for cooling water or some other fluid coolant.

As shown in FIG. 10, a system is provided for circulating cooling wateror some other fluid coolant through all of the coolant passages in thefurnace shell 20. The main supply of the cooling water is connected tothe circumferential passage 126 at the upper end of the upper wallsection 26, through a valve 142 and a main inlet pipe 146 connected toan inlet fitting 148. In addition to cooling the flange 124, thecircumferential passage 126 serves as a supply header from which variousbranch cooling pipes and hoses receive their cooling water.

The passage 126 extends entirely around the upper end of the top wallsection 26, except for a bulkhead 150 and walls 152 and 154 where themetal casing 40 is split initially for ease in shipment. When thefurnace shell is assembled, the split portions of the metal casing40,are welded or otherwise secured together at the walls 152 and 154.External bypass conduits 156 and 158 are provided to carry the coolingwater around the walls 152 and 154.

The circumferential cooling passage 134 is also interrupted by thevertical walls 152 and 154 where the metal casing 40 is initially splitfor shipment. External bypass conduits 160 and 162 are provided to carrythe cooling water around the walls 152. The passage 134 has an inlet 164which is supplied with cooling water from an outlet 166 connected to thepassage 126. A conduit 168 and valves 170 and 172 may be connectedbetween the outlet 166 and the inlet 164. The water travels through thecircumferential passage 134, including the bypass conduits 160 and 162,and is discharged from an outlet 174 into an outlet pipe 176 which maybe connected to a collector or bosh tank from which the water isrecycled or drained away.

Another outlet 178 is provided from the circumferential passage 126 tosupply the cooling water to each of the passages 138. A valve 180 and aconduit 182 are connected between the outlet 178 and the passage 138.The other end of each passage 138 leads to an outlet 184 connected toanother outlet pipe 186 which may lead to the collector tank.

The side member 104 is supplied with water from an outlet 188 connectedto the circumferential passage 126. A conduit 190 leads from the outlet188 to the side member 104. After passing through the member 104, thewater is discharged to an outlet pipe 192 which may be connected to thecollector tank.

Similarly, the other side member 106 is supplied with water by a conduit194 connected to an outlet 196 from the passage 126. The water from theside member 106 is discharged to an outlet pipe 198.

As illustrated in FIG. 10, the top member 108, positioned in the slagdischarge opening 100, is provided with two inlets 200 and 202 which areconnected to outlets 204 and 206, leading from the circumferentialpassage 126. A conduit 208 and a valve 210 are connected between theoutlet 204 and the inlet 200. Similarly, a conduit 212 and a valve 214are connected between the outlet 206 and the inlet 202. After passingthrough the top member 108, the water is discharged to outlet pipes 216and 218.

The door 102 is preferably provided with a hollow shaft 220 which issupplied with cooling water by a valve 222 and a conduit 224 connectedto an outlet 226 from the passage 126. The water passes from the hollowshaft 220 to the door 102 through a hose or flexible conduit 228. Afterpassing through the coolant passages in the door 102, the water isdischarged to outlet hose or conduit 230.

Elements are preferably provided on the wall sections 24 and 26 for theattachment of a lifting bail or some other lifting device. As shown inH65. 7 and 8, the middle wall section 24 may be provided with two pairsof lifting elements 232 and 234. Each of the illus-- trated liftingelements 232 comprises a pair of lugs or ribs 236 which are formed withopenings 238 adapted to receive pins or the like whereby lifting linksor other elements may be connected to the ribs236. Similarly, each ofthe lifting elements 234 comprises a pair of ribs or lugs 240 havingnotches or openings 242 therein to receive blocks 244, which may bewelded to the ribs 240. Openings 246 are formed in the blocks 244 toreceive a pin or the like whereby a link or other lifting device may beconnected to the lifting element 234.

Similarly, the illustrated top wall section 26 is formed with two pairsof lifting elements 248 and 250 which are similar to the liftingelements 232 and 234, respectively. The lifting elements on the middleand top wall sections 24 and 26 are positioned so that each wall sectionwill be properly balanced when it is being hoisted. In this way, eachwall section will hang level from the bail or other hoisting device.

FIGS. -17 illustrate an improved bail 260 which may be employed veryadvantageously for lifting the middle and top wall sections 24 and 26.The illustrated bail 260 comprises a generally horizontal frame 262having a main longitudinal member 264, end members 266 and 268 havingtheir central portions connected to the ends of the member 264, sidemembers 270 and 272 connected between the ends of the end members 266and 268, and intermediate members 274 and 276 extending outwardly fromthe main longitudinal member 264 and connected to the side members 270and 272. It will be seen that the end member 266 is considerably shorterthan the end member 268 so that the bail is non-symmetrical.

The bail 260 is adapted to be lifted by a crane or the like. Thus, amain lifting loop or eye 278 projects upwardly from the mainlongitudinal member 264. It will be understood that the loop 278 isadapted to receive the lifting hook 280 of a crane or the like.

In this case, the bail 260 also includes a secondary lifting device inthe form of a loop or eye 282, projecting upwardly from the mainlongitudinal member 264, at a point thereon between the primary liftingdevice 278 and the end member 268. The secondary lifting device 282 maybe employed to assist in leveling or Controlling the load on the bail260.

In order to provide for the lifting of the wall sections 24 and 26, theillustrated bail 260 is provided with two pairs of suspension devices284 and 284a, connected to the ends of the end members 266 and 268, andextending downwardly therefrom.

Each of the suspension devices 284 preferably comprises an adjustablemember 288 having a screwthreaded portion 290 received in a threadedsocket member 292 mounted on one end of the end member 266. The upperend of a connecting link 294 is connected to a forked portion 296 at thelower end of the member 288 by means of a pin or bolt 298 extendingthrough appropriate openings in the link 294 and forked portion 296.

Similarly, each of the suspension devices 284a comprises an adjustablemember 288a having a threaded portion 290a, a threaded socket member22a. a link 294a, a forked portion 296a, and a pin or bolt 298a. Thesocket members 292a are mounted on the ends of the end member 268.

In order that the wall sections 24 and 26 of the furnace shell 20 mayhang level from the bail 260, the suspension devices 284 are closertogether than the suspension devices 284a. Moreover, the suspensiondevices 284 are farther from the principal lifting device 278 than arethe suspension devices 2840. It will be seen that the distance betweenthe principal lifting device 278 and the end member 266 is greater thanthe distance between the lifting device 278 and the end member 268.

Each of the suspension devices 284 is displaced by an angle of about 30from the longitudinal member 264 relative to the principal liftingdevice 278. On the other hand, each of the suspension devices 284a isdisplaced by an angle of about 45 from the longitudinal member 264. Whenthe bail 260 is employed to lift the middle wall section 24, the links294 of the suspension devices 284 are connected to the lifting elements232, while the links 284a of the suspension devices 284a are connectedto the lifting elements 234. In this way, the center oflift representedby the principal lifting device 278 is displaced from the geometricalcenter of the wall section 24 toward the pouring spout 60 to allow forthe added weight of the pouring spout. Thus, the center of lift isaligned with the center of gravity of the wall section 24 so that itwill hang level from the bail 260. It will be seen that the liftingelements 232 on the middle wall section 24 are closer together than thelifting elements 234.

When the bail 260 is employed to lift the top wall section 26, theorientation of the ball is reversed so that the links 294 of thesuspension devices 284 are connected to the lifting elements 248, whilethe links 294a of the suspension devices 284a are connected to the elements 250. In this way, the center of lift represented by the principallifting device 278 is shifted toward the slag door 102 and the apron 114which contribute extra weight to the corresponding side of the top wallsection 26. Here again, the center of lift corresponds with the centerof gravity of the top wall section 26 so that it will hang level fromthe bail 260.

The ability of the bail 260 to support the wall sections 24 and 26 in alevel manner is important because the level position of each wallsection makes it easy to lower the wall section into place on thefurnace shell without damaging the previously installed refractorylining. The reversible non-symmetrical bail 260 makes it possible tolift both of the wall sections 24 and 26 in a level manner despite thedifferences in the locations of the centers of gravity of the two wallsections.

In operation, the furnace shell 20 may be employed for melting steelscrap or for various other purposes. The steel scrap is charged into thefurnace shell from the top thereof. The heat to melt the steel issupplied by electric arcs drawn between electric arc electrodes,

the refractory lining 64 in the pouring spout 60. Molten slag may beremoved by tipping or rocking the furnace shell in the oppositedirection, while opening the door 102 so that the slag will be pouredthrough the opening 100. The slag flows over the graphite'blocks 118which line the apron 114. The graphite blocks 1 18 withstand the heat ofthe slag and prevent the slag from adhering to the apron 114.

During the operation of the furnace, cooling water is circulated throughthe slag door 102 and also through the members 104, 106 and 108 whichare employed to line the slag discharge opening 100. These members arethereby protected from damage due to the heat generated in the furnaceshell 20. Cooling water is also circulated through the passages 126, 134and 140 in the top wall section 126. The passages 134 and 140 extendalong the joint between the top wall section 26 and the middle wallsection 24 so as to prevent damage to the furnace if there is anyleakage of heat through the joint. The passage 126 extends around theupper end of the top wallsection 26 where it is engaged by the roof orcover. Thus, the cooling passage 126 prevents damage to the furnace dueto any possible leakage of heat at this point.

As the furnace shell 20 is used, the refractory lining is graduallyconsumed so that eventually it becomes necessary to replace the lining.The refractory linings 38 and 42 of the wall sections 24 and 26 aresubject to greater attrition and damage then the refractory lining ofthe bottom section 22 because the refractory linings of the wallsections 24 and 26 are subject to more intense heat and greater thermalshock. Consequently, the lining 30 of the bottom section 22 may outlasttwo or more linings of the wall sections 24 and 26.

It is preferred to provide a set of spares for the wall sections 24 and26. During the normal use of the furnace shell 20, the refractorylinings 38 and 42 are installed in the spare wall sections 24 and 26.The linings 38 and 42 are supported by the ledges 90, 92 and 94projecting inwardly at the lower ends of the wall sections 24 and 26.

When it becomes necessary to shut down the furnace to replace therefractory linings, the old wall sections 24 and 26 are removed from thefurnace shell 20 by the use of the bail 260 anda suitable crane orhoist. The spare wall sections 24 and 26 complete with their refractorylinings 38 and 42 are then hoistedinto place on the furnace shell. Thetapered pins 52 and 86 insure that the wall sections 24 and 26 will bemaintained in alignment with the bottom section 22. Fireclay or someother refractory material is employed to close and seal the jointsbetween the refractory linings 30, 38 and 40. The furnace shell 20 isthen put back into service. While the furnace is in service, therefractory linings 38 and 42 of the original wall sections 24 and 26 arereplaced so that these wall sections will be ready for installation onthe furnace shell 20.

It will be evident that the furnace shell construction of the presentinvention makes it possible to replace the refractory lining of thefurnace shell with only a very brief shutdown of the furnace.

I claim:

1. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom section having a metal casingand a refractory lining,

a first generally ring-shaped wall section removably mounted on top ofsaid bottom section and having a metal casing and a refractory lining,

and a second generally ring-shaped wall section removably mounted on topof said first wall section and having a metal casing and a refractorylining,

each of said wall sections having means for supporting the refractorylining thereof when said wall section is dismounted from the furnaceshell,

whereby the refractory lining may be installed in each wall sectionprior to the mounting of the wall section on the furnace shell,

said first wall section having an upper portion with an upward stepadjacent one side of said first wall section,

said second wall section having a correspondingly stepped lower portionto mate with the stepped upper portion of said first wall section.

2. A furnace shell for use with molten metal, comprising a generallydish-shaped bottom section having a metal casing and a refractorylining,

a first generally ring-shaped wall section removably mounted on top ofsaid bottom section and having a metal casing and a refractory lining,

and a second generally ring-shaped wall section removably mounted on topof said first wall section and having a metal casing and a refractorylining,

each of said wall sections having means for supporting the refractorylining thereof when said wall section is dismounted from the furnaceshell,

whereby the refractory lining may be installed in each wall sectionprior to the mounting of the wall section on the furnace shell,

said first wall section being formed with a pouring opening therein forthe discharge of the molten metal from the furnace,

said first wall section having a pouring spout extending outwardlytherefrom opposite said pouring opening,

said first wall section having an upper portion which is steppedupwardly adjacent said pouring spout,

said second wall section having a correspondingly stepped lower portionto mate with the stepped upper portion of said first wall sectionwhereby molten metal can be poured from said' pouring spout withoutcausing the molten metal to rise above the stepped joint between saidfirst and second wall sections.

3. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom section including a metalcasing for receiving a refractory lining,

a first generally ring-shaped wall section removably mounted on top ofsaid bottom section and including a metal casing for receiving arefractory lining,

said wall section having means for supporting a refractory liningtherein when said wall section is dismounted from the furnace shell,

whereby the refractory lining may be installed in said wall sectionprior to the mounting of the wall section on the furnace shell,

and a second generally ring-shaped wall section removably mounted on topof said first wall section and including a metal casing for receiving arefractory lining,

said first wall section being formed with a discharge opening throughwhich the molten metal may be poured,

said first wall section-having an upwardly stepped upper portionadjacent said opening,

said second wall section having a stepped lower portion to mate withsaid stepped upper portion of said first wall section whereby the jointbetween said first and second wall sections will remain above the levelof the molten metal even when the furnace is tipped to pour out themolten metal.

4. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom section having a metal casingand a refractory lining,

a first generally ring-shaped wall section removably mounted on top ofsaid bottom section and having a metal casing and a refractory lining,

and a second generally ring-shaped wall section removably mounted on topof said first wall section and having a metal casing and a refractorylining,

said first wall section having a pouring opening therein for thedischarge of the molten metal from the furnace,

said first wall section having an upper portion which is steppedupwardly adjacent said pouring opening,

said second wall section having a correspondingly stepped lower portionto mate with the stepped upper portion of said first wall sectionwhereby molten metal can be poured from said pouring opening withoutcausing the molten metal to rise above the stepped joint between saidfirst and second wall sections.

5. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom section including a metalcasing for receiving a refractory lining,

a first generally ring-shaped wall section removably mounted on top ofsaid bottom section and including a metal casing for receiving arefractory lining,

and a second generally ring-shaped wall section removably mounted on topof said first wall section and including a metal casing for receiving arefractory lining,

said first wall section being formed with a discharge opening throughwhich the molten metal may be poured,

said first wall section having an upwardly stepped upper portionadjacent said opening,

said second wall section having a stepped lower portion to mate withsaid stepped upper portion of said first wall section whereby the jointbetween said first and second wall sections will remain above the levelof the molten metal even when the furnace is tipped to pour out themolten metal.

6. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom section including a metalcasing for receiving a refractory lining,

a first generally ring-shaped wall section removably mounted on top ofsaid bottom section and including a metal casing for receiving arefractory lining,

and a second generally ring-shaped wall section removably mounted on topof said first wall section and including a metal casing for receiving arefractory lining,

said first wall section having an upwardly stepped upper portionadjacent one side of said first wall section,

said second wall section having a correspondingly stepped lower portionto mate with said stepped upper portion of said first wall section.

7. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom wall portion,

a generally ring-shaped side wall portion extending upwardly from saidbottom wall portion,

and a generally ring-shaped upper wall section removably mounted on topof said side wall portion,

said side wall portion being formed with a discharge opening throughwhich the molten metal may be poured,

said side wall portion having an upwardly stepped upper portion adjacentsaid opening,

said upper wall section'having a stepped lower portion to mate with saidstepped upper portion of said side wall portion whereby the jointbetween said side wall portion and said upper wall section will remainabove the level of the molten metal even when the furnace is tipped topour out the molten metal. I

8. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom wall portion,

a generally ring-shaped side wall portion extending upwardly from saidbottom wall portion,

and a generally ring-shaped upper wall section removably mounted on topof said side wall portion,

said side wall portion having an upwardly stepped upper portion adjacentone side of said side wall portion,

said upper wall section having a correspondingly stepped lower portionto mate with said stepped upper portion of said side wall portion.

9. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom wall portron,

a generally ring-shaped side wall portion extending upwardly from saidbottom wall portion,

and an upper wall portion mounted on top of said side wall portion,

said side wall portion being formed with a discharge opening throughwhich the molten metal may be poured,

said side wall portion having an upwardly stepped upper portion adjacentsaid opening,

said upper wall portion having a stepped lower portion to mate with saidstepped upper portion of said Side wall portion whereby the jointbetween said side wall portion and said upper wall portion can remainabove the level of the molten metal even when the furnace is tipped topour out the molten metal.

10. A furnace shell for use with molten metal,

comprising a generally dish-shaped bottom portion,

a side wall portion extending upwardly from said bottom wall portion,

and an upper wall portion mounted on top of said side wall portion,

said side wall portion having an upwardly stepped upper portion adjacentone side of said side wall portion,

said upper wall portion having a correspondingly stepped lower portionto mate with said stepped upper portion of said side wall portion;

11. A furnace shell for use with molten metal, comprising a generallydish-shaped bottom portion including a metal casing with a refractorylining,

a generally ring-shaped side wall portion extending upwardly from saidbottom portion and including a metal casing with a refractory lining,

and an upper generally ring-shaped wall portion mounted on top, of saidside wall portion and including a metal casing with a refractory lining,

said side wall portion being formed with a discharge opening throughwhich the molten metal may be poured,

said side wall portion having an upwardly stepped upper portion adjacentsaid opening,

said upper wall portion having a stepped lower portion to mate with saidstepped upper portion of said side wall portion whereby the jointbetween said side wall portion and said upper wall portion will remainabove the level of the molten metal even when the furnace is tipped topour out the molten metal.

12. A furnace shell for use with molten metal, comprising a generallydish-shaped bottom portion including a metal casing with a refractorylining,

a generally ring-shaped side wall portion extending upwardly from saidbottom section and including a metal casing with a refractory lining,

and an upper generally ring-shaped wall portion mounted on top of saidside wall portion and including a metal casing with a refractory lining,

said side wall portion having an upwardly stepped upper portion adjacentone side of said side wall portion,

said upper wall portion having a stepped lower portion to mate with saidstepped upper portion of said side wall portion.

1. A furnace shell for use with molten metal, comprising a generallydish-shaped bottom section having a metal casing and a refractorylining, a first generally ring-shaped wall section removably mounted ontop of said bottom section and having a metal casing and a refractorylining, and a second generally ring-shaped wall section removablymounted on top of said first wall section and having a metal casing anda refractory lining, each of said wall sections having means forsupporting the refractory lining thereof when said wall section isdismounted from the furnace shell, whereby the refractory lining may beinstalled in each wall section prior to the mounting of the wall sectionon the furnace shell, said first wall section having an upper portionwith an upward step adjacent one side of said first wall section, saidsecond wall section having a correspondingly stepped lower portion tomate with the stepped upper portion of said first wall section.
 2. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom section having a metal casing and a refractorylining, a first generally ring-shaped wall section removably mounted ontop of said bottom section and having a metal casing and a refractorylining, and a second generally ring-shaped wall section removablymounted on top of said first wall section and having a metal casing anda refractory lining, each of said wall sections having means forsupporting the refractory lining thereof when said wall section isdismounted from the furnace shell, whereby the refractory lining may beinstalled in each wall section prior to the mounting of the wall sectionon the furnace shell, said first wall section being formed with apouring opening therein for the discharge of the molten metal from thefurnace, said first wall section having a pouring spout extendingoutwardly therefrom opposite said pouring opening, said first wallsection having an upper portion which is stepped upwardly adjacent saidpouring spout, said second wall section having a correspondingly steppedlower portion to mate with the stepped upper portion of said first wallsection whereby molten metal can be poured from said pouring spoutwithout causing the molten metal to rise above the stepped joint betweensaid first and second wall sections.
 3. A furnace shell for use withmolten metal, COMPRISING a generally dish-shaped bottom sectionincluding a metal casing for receiving a refractory lining, a firstgenerally ring-shaped wall section removably mounted on top of saidbottom section and including a metal casing for receiving a refractorylining, said wall section having means for supporting a refractorylining therein when said wall section is dismounted from the furnaceshell, whereby the refractory lining may be installed in said wallsection prior to the mounting of the wall section on the furnace shell,and a second generally ring-shaped wall section removably mounted on topof said first wall section and including a metal casing for receiving arefractory lining, said first wall section being formed with a dischargeopening through which the molten metal may be poured, said first wallsection having an upwardly stepped upper portion adjacent said opening,said second wall section having a stepped lower portion to mate withsaid stepped upper portion of said first wall section whereby the jointbetween said first and second wall sections will remain above the levelof the molten metal even when the furnace is tipped to pour out themolten metal.
 4. A furnace shell for use with molten metal, comprising agenerally dish-shaped bottom section having a metal casing and arefractory lining, a first generally ring-shaped wall section removablymounted on top of said bottom section and having a metal casing and arefractory lining, and a second generally ring-shaped wall sectionremovably mounted on top of said first wall section and having a metalcasing and a refractory lining, said first wall section having a pouringopening therein for the discharge of the molten metal from the furnace,said first wall section having an upper portion which is steppedupwardly adjacent said pouring opening, said second wall section havinga correspondingly stepped lower portion to mate with the stepped upperportion of said first wall section whereby molten metal can be pouredfrom said pouring opening without causing the molten metal to rise abovethe stepped joint between said first and second wall sections.
 5. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom section including a metal casing for receiving arefractory lining, a first generally ring-shaped wall section removablymounted on top of said bottom section and including a metal casing forreceiving a refractory lining, and a second generally ring-shaped wallsection removably mounted on top of said first wall section andincluding a metal casing for receiving a refractory lining, said firstwall section being formed with a discharge opening through which themolten metal may be poured, said first wall section having an upwardlystepped upper portion adjacent said opening, said second wall sectionhaving a stepped lower portion to mate with said stepped upper portionof said first wall section whereby the joint between said first andsecond wall sections will remain above the level of the molten metaleven when the furnace is tipped to pour out the molten metal.
 6. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom section including a metal casing for receiving arefractory lining, a first generally ring-shaped wall section removablymounted on top of said bottom section and including a metal casing forreceiving a refractory lining, and a second generally ring-shaped wallsection removably mounted on top of said first wall section andincluding a metal casing for receiving a refractory lining, said firstwall section having an upwardly stepped upper portion adjacent one sideof said first wall section, said second wall section having acorrespondingly stepped lower portion to mate with said stepped upperportion of said first wall section.
 7. A furnace shell for use withmolten metal, comprising a generally Dish-shaped bottom wall portion, agenerally ring-shaped side wall portion extending upwardly from saidbottom wall portion, and a generally ring-shaped upper wall sectionremovably mounted on top of said side wall portion, said side wallportion being formed with a discharge opening through which the moltenmetal may be poured, said side wall portion having an upwardly steppedupper portion adjacent said opening, said upper wall section having astepped lower portion to mate with said stepped upper portion of saidside wall portion whereby the joint between said side wall portion andsaid upper wall section will remain above the level of the molten metaleven when the furnace is tipped to pour out the molten metal.
 8. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom wall portion, a generally ring-shaped side wallportion extending upwardly from said bottom wall portion, and agenerally ring-shaped upper wall section removably mounted on top ofsaid side wall portion, said side wall portion having an upwardlystepped upper portion adjacent one side of said side wall portion, saidupper wall section having a correspondingly stepped lower portion tomate with said stepped upper portion of said side wall portion.
 9. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom wall portion, a generally ring-shaped side wallportion extending upwardly from said bottom wall portion, and an upperwall portion mounted on top of said side wall portion, said side wallportion being formed with a discharge opening through which the moltenmetal may be poured, said side wall portion having an upwardly steppedupper portion adjacent said opening, said upper wall portion having astepped lower portion to mate with said stepped upper portion of saidside wall portion whereby the joint between said side wall portion andsaid upper wall portion can remain above the level of the molten metaleven when the furnace is tipped to pour out the molten metal.
 10. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom portion, a side wall portion extending upwardly fromsaid bottom wall portion, and an upper wall portion mounted on top ofsaid side wall portion, said side wall portion having an upwardlystepped upper portion adjacent one side of said side wall portion, saidupper wall portion having a correspondingly stepped lower portion tomate with said stepped upper portion of said side wall portion.
 11. Afurnace shell for use with molten metal, comprising a generallydish-shaped bottom portion including a metal casing with a refractorylining, a generally ring-shaped side wall portion extending upwardlyfrom said bottom portion and including a metal casing with a refractorylining, and an upper generally ring-shaped wall portion mounted on topof said side wall portion and including a metal casing with a refractorylining, said side wall portion being formed with a discharge openingthrough which the molten metal may be poured, said side wall portionhaving an upwardly stepped upper portion adjacent said opening, saidupper wall portion having a stepped lower portion to mate with saidstepped upper portion of said side wall portion whereby the jointbetween said side wall portion and said upper wall portion will remainabove the level of the molten metal even when the furnace is tipped topour out the molten metal.
 12. A furnace shell for use with moltenmetal, comprising a generally dish-shaped bottom portion including ametal casing with a refractory lining, a generally ring-shaped side wallportion extending upwardly from said bottom section and including ametal casing with a refractory lining, and an upper generallyring-shaped wall portion mounted on top of said side wall portion andincluding a metal casing with a refractory lining, SAID side wallportion having an upwardly stepped upper portion adjacent one side ofsaid side wall portion, said upper wall portion having a stepped lowerportion to mate with said stepped upper portion of said side wallportion.